1. Field of the Invention
The present invention relates to an electron emission display device and a method of correcting an image signal, and more specifically to an electron emission display device and a method of correcting an image signal to enhance an image quality by reducing or preventing luminance unevenness among pixels.
2. Discussion of Related Art
In general, electron emitting parts used for electron emission display devices can be classified into electron emitting parts in which hot cathode rays are used as electron sources and electron emitting parts in which cold cathode rays are used as electron sources. The electron emitting parts in which the cold cathodes are used include field emitter array (FEA) type electron emitting parts, surface conduction emitter (SCE) type electron emitting parts, metal-insulator-metal (MIM) type electron emitting parts, metal-insulator-semiconductor (MIS) type electron emitting parts, and ballistic electron surface emitting (BSE) type electron emitting parts.
The FEA type of the electron emission display device uses a principle that emits electrons by electric field difference in vacuum by using materials with a low work function or a high β function as an electron emission source, wherein any device using a tip structure of which leading is sharp or carbon-based materials or nano-based materials as an electron emission source is developing.
The SCE type of the electron emission display device is a device that an electron emitting part is formed by providing a conductive thin film between two electrodes arranged to be opposed to each other on a substrate and finely cracking the conductive thin film. The device uses a principle that voltage is applied to the electrodes to flow current onto the surface of the conductive thin film, thereby emitting electrons from the electron emitting part being a fine gap.
The MIM and the MIS types of the electron emission display devices form electron emitting parts configured of a metal-insulator metal (MIM) and a metal-insulator-semiconductor (MIS) structures, respectively, wherein it is a device using a principle that when voltage is applied to two metals having an insulator positioned therebetween or between a metal and a semiconductor, electrons are emitted by moving and accelerating them from the metal and the semiconductor having a high electron potential to the metal having a low electron potential.
The BSE type of the electron emission display device is a device emitting electrons by forming an electron supplying layer configured of a metal or a semiconductor on an ohmic electrode and forming an isolating layer and a metal thin film on the electron supplying layer, and then applying a power source to the ohmic electrode and the metal thin film, using a principle traveling without scattering electrons in the case that the size of the semiconductor is reduced up to a dimensional range smaller than an average free stroke of electrons.
Such electron emission display devices can be used in various fields and have vigorously been studied up to recently, due to advantages that likewise a cathode-ray-tube (CRT), it is operated by light-emitting a cathode electrode wire (self-light source, high efficiency, high luminance and wide luminance range, natural color and high color purity, wide viewing angle), and its operation speed and operation temperature range, etc., are wide.
FIG. 1 is a structural view illustrating a conventional electron emission display device. Referring to FIG. 1, the electron emission display device includes a display region 10, a data driver 20, a scan driver 30, and a timing controller 40.
In the display region 10, pixels 10 are located at regions defined by the crossings (or intersections) of cathode electrodes C1, C2, . . . , Cm and gate electrodes G1, G2, . . . , Gn. The pixels 10 include electron emitting parts so that electrons emitted from the electron emitting parts on the cathode electrodes collide with an anode electrode having a high voltage level to light-emit phosphors for displaying an image. The gray levels of images displayed vary depending on input digital image signal values. To control the gray levels represented depending on the digital image signal values, a pulse width modulation scheme can be used. The pulse width modulation scheme is a scheme to control a time period that a data signal of a constant voltage is applied to one or more of the cathode electrodes such that a long time period is used to represent a high gray level and a short time period is used to represent a low gray level.
The data driver 20 uses an image signal to generate a data signal and is connected to the cathode electrodes C1, C2, . . . , Cm to transfer the data signal to the display region 10 so that the display region 10 is light-emitted depending on the data signal.
The scan driver 30 is connected to the gate electrodes G1, G2, . . . , Gn to generate a scan signal and transfers it to the display region 10 so that the display region 10 is sequentially light-emitted using a line scan scheme in units of horizontal lines with uniform time period to display an entire image on the display region 10.
The timing controller 40 transfers an image signal, a data driver controlling signal, a scan driver controlling signal, etc., to the data driver 20 and the scan driver 30 to operate the data driver 20 and the scan driver 30 to display an image on the display region 10.
In an electron emission display device as described above, a plurality of electron emitting parts are positioned at a plurality of pixels, respectively, and the luminance of the pixels depends on the amount of electrons emitted from the plurality of electron emitting parts. However, the electron emitting parts may be non-uniformly manufactured to cause the amount of electrons emitted from each of the electron emitting parts to be different even when the same image signal is input into each of the electron emitting parts, resulting in that the luminance of each of the pixels is different.